This invention relates to containers for highly corrosive solutions and more particularly to containers for use in the electrolytic refinement or electrowinning of metals such as copper.
In one type of process, the refinement of metals such as copper, a substantially pure copper anode is immersed in a suitable electrolyte, such as, a hydrochloric or sulphuric acid solution. The copper is deposited in a pure form on a cathode when an electric current is passed between the electrodes.
One type of prior art container employed for such electrolytic cells consists of a concrete shell having iron reinforcing bars and a lead or plastic liner. Such containers were not wholly satisfactory because the linings often failed causing the concrete to fail before the leaks were detected resulting in the loss of slimes and electrolyte. For this reason prior art concrete cells required high maintenance, high repair and replacement costs and caused excessive downtime and lost production. In addition, the iron reinforcing bars provide a leakage path to stray electric currents which reduced current efficiency and affected cathode quality. Furthermore, because prior cells tended to absorb highly toxic materials, environmental concerns result in high disposal costs. One prior art effort to improve such electrolytic cells included a shell fabricated from a mixture of about 20 percent in and 80 percent various aggregates such as pea size gravel, fine silica sand, silica flour and one-quarter to one-eighth inch chopped fiberglass strands. These prior art cells had the disadvantage of relatively high fabrication costs, and a susceptibility to short circuiting as a result of the use of reinforcing rods which include ferrous materials. Another disadvantage of prior art cells was that the molding process by which they were formed resulted in cold joints, irregular internal surfaces and required that overflow boxes be separately attached.